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Math Help - roots of the quadratic equation

  1. #1
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    roots of the quadratic equation

    Given the root of the quadratic equation of 4ax^2+bx+8=0 are equal.Express a in terms of b
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  2. #2
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    Quote Originally Posted by lindros View Post
    Given the root of the quadratic equation of 4ax^2+bx+8=0 are equal.Express a in terms of b
    The question tells you that 4ax^2+bx+8=0 is a square (the square of a linear term) , now try it and if you have further problems post what you have tried or what you do not understand

    CB
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  3. #3
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    You know the quadratic formula, don't you: x= \frac{-b\pm\sqrt{b^2- 4ac}}{2a}

    The two roots will be equal if and only if the square root is 0.

    Another way to do this is to write the equation as 4ax^2+ bx+ 8= 4a(x- x_0)(x- x_0). Multiply the right side and set corresponding coefficients equal.
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  4. #4
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    Quote Originally Posted by lindros View Post
    Given the root of the quadratic equation of 4ax^2+bx+8=0 are equal.Express a in terms of b

    Use the following: if \alpha\,,\,\beta are the roots of ax^2+bx+c=0\,,\,\,a\neq 0 , then \alpha\beta=\frac{c}{a}\,,\,\,\alpha+\beta=-\frac{b}{a} .

    You can also google "Viete's formulae"

    Tonio
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